On the mechanism of ring opening in 2-pyrone irradiations

Guthrie, J. Peter; McIntosh, C. L.; Mayo, P. De

doi:10.1139/v70-038

Cited by 28 publications

(23 citation statements)

References 7 publications

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“…δ(C-CH 3 ) as S 20 = (12 −1/2 )(β 9,10,6 + β 10,11,6 + β 11,9,6 − β 9,3,6 − β 10,3,6 − β 11,3,6 + β 12 …”

Section: Resultsunclassified

“…ν(C3-C4) S 4 = r 4,5 ν(C4=C5) S 5 = r 5,6 ν(C5-C6) S 6 = r 6,1 ν(C6-O1) S 7 = r 3,6 ν(C3-C6) S 8 = r 7,2 ν(C2=O7) S 9 = r 8,6 ν(C6-C8) S 10 = (3 −1/2 )(r 9,8 + r 10,8 + r 11,8 …”

Section: Computational Detailsunclassified

“…δ(C2=O7) S 22 = β 8,3,6 δ(C6-C8) S 23 = (6 −1/2 )(β 9,10,8 + β 10,11,8 + β 11,9,8 − β 9,6,8 given in Tables 1-3. The calculated harmonic frequencies were also used to assist the analysis of the experimental spectra and to confirm the nature of the stationary points resulting from the calculations (for all structures discussed below no imaginary frequencies were obtained, indicating they correspond to true minima).…”

Section: Computational Detailsmentioning

confidence: 99%

“…In the study of UV irradiated thin solid films layers of 4,6-dimethyl-␣-pyrone at −190 • C, Guthrie et al [6] were able to observe IR bands that could be attributed to both photoproducts: Dewar valence isomer and conjugated aldehyde-ketene. This result indicated that both species could indeed be photoproduced from the reactant molecule.…”

Section: Introductionmentioning

confidence: 99%

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4,6-Dimethyl-α-pyrone: a matrix isolation study of the photochemical generation of conjugated ketene, Dewar valence isomer and 1,3-dimethyl-cyclobutadiene

Breda

Lapiński

Reva

et al. 2004

Journal of Photochemistry and Photobiology A: Chemistry

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A combined matrix isolation and molecular orbital study of the vibrational spectra and photochemistry of 4,6-dimethyl-␣-pyrone (DMAP) was undertaken. Two types of photoreactions: ring opening leading to conjugated ketene and valence isomerization to the Dewar form (1,5-dimethyl-2-oxa-3-oxobicyclo[2.2.0]hex-5-ene; DOOBH), occurred upon UV (λ > 315 nm) irradiation. The latter reaction was efficient, whereas aldehyde-ketene was produced only in little amounts. In addition to the IR spectroscopic study of DMAP, the full mid-IR spectrum of the photoproduced DOOBH is reported and interpreted. Observation of 1,3-dimethyl-cyclobutadiene (DMCB), created by shorter wavelength UV irradiation (λ > 235 nm) of DOOBH, is reported for the first time. In the matrices, DMCB forms a complex with CO 2 ; the structure and IR absorption features of this cage confined DMCB-CO 2 complex are also investigated.

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“…δ(C-CH 3 ) as S 20 = (12 −1/2 )(β 9,10,6 + β 10,11,6 + β 11,9,6 − β 9,3,6 − β 10,3,6 − β 11,3,6 + β 12 …”

Section: Resultsunclassified

“…ν(C3-C4) S 4 = r 4,5 ν(C4=C5) S 5 = r 5,6 ν(C5-C6) S 6 = r 6,1 ν(C6-O1) S 7 = r 3,6 ν(C3-C6) S 8 = r 7,2 ν(C2=O7) S 9 = r 8,6 ν(C6-C8) S 10 = (3 −1/2 )(r 9,8 + r 10,8 + r 11,8 …”

Section: Computational Detailsunclassified

Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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4,6-Dimethyl-α-pyrone: a matrix isolation study of the photochemical generation of conjugated ketene, Dewar valence isomer and 1,3-dimethyl-cyclobutadiene

Breda

Lapiński

Reva

et al. 2004

Journal of Photochemistry and Photobiology A: Chemistry

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“…Methanol addition to 22 followed by thermal conrotatory 6At this point in our investigations a private communication from Professor de Mayo described his recent studies on the photochemical behavior of 4-methoxy-6-methyl-2-pyrone (12) in water and benzene. We thank Professor de Mayo for informing us of his results prior to publication (6).…”

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confidence: 99%

Pyrone studies. Photochemistry of triacetic acid lactone

Bedford¹,

Forrester²,

Money³

1970

Can. J. Chem.

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The irradiation of triacetic acid lactone in various solvents results in novel rearrangement to b-methylglutaconic acid derivatives. In benzene solution an efficient conversion to p-methylglutaconic acid anhydride occurs while in methanol solution a mixture of products is obtained whose structures represent retention and rearrangement of the original carbon skeleton. Results obtained from irradiation of the corresponding methyl ether of triacetic acid lactone in methanol solution are also described.Canadian Journal of Chemistry, 48, 2645 (1970) In connection with our studies of ring cleavagearomatization reactions of pyrones and polypyrones (2) we have recently investigated the photolysis of some suitable 2-pyrone systems. 4-Hydroxy-6-methyl-2-pyrone (3) (triacetic acid lactone, TAL) and its methyl ether, 12, were chosen as simple analogs of a series of compounds we wished to study and this paper describes the photochemistry of these compounds in different solvents. Pertinent to this study were the previous results of de Mayo and his colleagues (3) who demonstrated that irradiation of 4,6-dimethyl-2-pyrone (1) in methanol solution affords methyl P-acetonylcrotonate (2) (see Scheme 1). A keten (5) and by de Mayo and his coworkers (6) support the original view (3) that keten (la) is an intermediate in this reaction.At the outset of our investigations we considered that a similar photochemical process would efficiently convert triacetic acid lactone 3 into methyl 3,5-dioxohexanoate (4b), and, by extension, other 2-pyrone systems into poly-Pketo esters of varying chain length (Scheme 2).In our initial experiment irradiation of a 0.1 % methanolic solution of TAL for 3 h at room temperature and examination of the reaction mixture by thin-layer chromatography (t.1.c.) showed that complete conversion to a mixture of products had o c c~r r e d .~ Careful removal of solvent and steam distillation of an aqueous solution (pH 6.3) of the residue afforded a distillate from which methyl 3,5-dioxohexanoate (4b) was isolated as a colorless oil. The nuclear magnetic resonance (n.m.r.) spectrum of this product showed that it existed as a tautomeric mixture of keto 4b and en01 4a forms. In an alternative work-up of the evaporated reaction mixture crystallization from ether-petroleum ether yielded cis-P-methoxycarbonylmethylcrotonic

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